China's central bank cut interest rates and lowered the amount of reserves banks must hold for the second time in two months on Tuesday, ratcheting up support for a stuttering economy and a plunging stock market that has sent shockwaves around the globe.

Chinese stocks fell on Tuesday, taking little comfort from a slew of support measures unleashed by Beijing in recent days, and unnerved by Chinese Premier Li Keqiang's failure to mention the market chaos in a statement on the economy.

Chinese stocks tumbled again on Friday, taking the week's losses to more than 10 percent, as the securities regulator said it was investigating suspected market manipulation and announced a slew of measures aimed at heading off a full-blown crash.

Chinese stocks plunged over 7 percent on Friday, with one key index recording its biggest fall since 2008, hit by tight liquidity conditions ahead of the quarter-end and uncertainty over the central bank's easing policy.

DuPont repelled a board challenge from activist investor Nelson Peltz on Wednesday, dealing him a surprising blow after shareholders backed all 12 directors nominated by the U.S. chemical conglomerate's management.